The accumulation of medical evidence in recent years regarding the adverse health implications of high fat diets, principally heart attacks, atherosclerosis and overweight, has created a heightened consumer awareness and concern of diet and caloric intake. Common obesity is one of the most prevalent metabolic disorders afflicting people today. It is estimated that between 70-80% of U.S. adult females follow a weight reducing diet at least once a year. The concerns of both men and women have given rise to diet fads, diet drinks (most noticeably in the soft drink, wine and beer industry), exercise programs and health clubs.
Although fats and oils are necessary for balanced nutrition, the average consumer simply ingests more than is required for proper nutrition. Fat, at 9 calories per gram, as compared to carbohydrates or proteins, at 4 calories per gram, is the most concentrated dietary energy form. It is estimated that fat constitutes approximately 40% of the total calories found in the typical western diet. Fats are consumed directly from meats, spreads, salad oils, and natural produce such as nuts and avocados. Fats and oils are consumed as a result of absorption or incorporation in the foods during baking and frying. The dramatic rise in popularity of "fast foods" in the U.S. has been a major contributor to the increase in the consumption of dietary fat since fast foods rely extensively on the frying process. In addition, the snack food industry uses large amounts of fats and oils in the production of potato chips, corn chips and other snack items. For example, in 1981 the USDA estimated approximately 12 billion pounds of fat and oil were used in edible products, predominately baking, frying fats, margarine, salad oil and/or cooking oil.
Many nutritionists believe that Americans typically rely on fats for a disproportionately large percentage of calories in their diet. The National Research Council, for example, has recommended that Americans reduce the proportion of their dietary calories coming from fats from 40% to at least 30%. Clearly an enormous potential exists in the health food industry for a fat substitute of fat mimetic that is either entirely indigestible, or has reduced caloric value. Replacement of fats in the diet with non-caloric substitutes is a more efficient means of reducing caloric intake than replacement of sugar or carbohydrates. In fact, gram for gram, the substitution of a fat mimetic into the diet is more than twice as effective than the reduction of carbohydrate content through the introduction of saccharine or Nutra-sweet.
One difficulty in eliminating fat from the diet comes from the fact that fats and oils are all-pervasive in modern food products. In part, this is because they play an important role in the organoleptic acceptability of food products. Consequently, fat mimetics must have good organoleptic qualities of mouth feel and be tasteless. Related to the aesthetic organoleptic qualities desired in a fat mimetic, substitutes must also have appropriate physical properties for use in food compositions. That is, they should be liquids or solids depending on whether they are used as oil or shortening substitutes. Where used for cooking, mimetics must be thermally stable. For example, while certain polysaccharide gums have been used as thickening agents, bulking agents or fillers in low-calorie foods, they can give a product a "slimy" mouth feel and are unsuitable for cooking as they have no thermal stability.
For a fat mimetic to be used as an acceptable substitute, it must be indigestible, that is, not hydrolyzed in the digestive tract, as well as unable to be directly absorbed through the intestinal wall. While some types of fat substitutes may be indigestible, they are not of sufficiently high molecular weight to prevent them from being absorbed through the intestinal wall. The threshold molecular weight of non-absorbability for lipophilic molecules appears to be about 600 amu.
The fat substitute must itself be non-toxic at high levels of ingestion. It must contain no toxic residues or impurities. To the extent that a fat substitute may be partially hydrolyzed in the digestive tract, any by-products of the hydrolysis must be non-toxic and/or capable of being metabolized. If the by-products are to be metabolized, they should have very low caloric value. In general, fat substitutes must be without any serious medical side affects.
Acceptable synthetic fats would be added in large quantities (30-60%) to salad oils, cooking oils, margarines, butter blends, mayonnaise, shortenings and the like to create a new class of low-calorie products. While "low calorie" mayonnaise and salad dressings are presently available, the reduction in calories is achieved by increasing the water content with a corresponding loss in the organoleptically "rich" taste of such products. The use of an effective fat mimetic would not require such a trade-off.
A current review of the field is found in a feature article entitled "Gettinq The Fat Out - Researchers Seek Substitutes For Full-Fat" JAOCS, Vol. 63, No. 3, (March 1986) pp. 278-286, 288. The article stresses the need to identify satisfactory means of reducing dietary fat intake stating that although media and various U.S. departments have recommended a decrease in consumption, actual per capita consumption has increased. Several methods for reducing dietary fat intake, including the use of fat substitutes, are discussed. Sugar polyesters, sucrose esters and branched polysaccharides are mentioned among the possible candidates for fat substitutes.
One prior art proposed fat substitute is sucrose polyester (SPE), shown in U.S. Pat. Nos. 3,600,186 (Matson, et al., 1971), 3,521,827 and 3 963,699 (Rizzi, et al., 1976) of Proctor & Gamble. The SPEs are produced by the reaction of a monosaccharide, disaccharide or sugar alcohol having a minimum of four hydroxyl groups with fatty acids having from 8-22 carbon atoms. It was reported in "Chemical and Engineering News" (July 26, 1982, page 32) that incorporating SPE as a partial replacement of the fats in the diets of ten obese patients dropped their caloric intake while satisfying their perceived need for fats. An additional benefit was the lowering of serum cholesterol, low density lipo-protein and triglycerides, all of which have been implicated in artery hardening diseases. However, SPE has the serious disadvantage of causing diarrhea, and plasma vitamin A and vitamin E levels are decreased.
Pat. No. 3,251,827 (Schnell et al.) discloses a preparation of SPE by means of a solvent-free interesterification using phenyl esters. However, phenol is liberated during the reaction. Since phenol is extremely toxic and caustic, it contaminates the product and is very difficult to separate. Accordingly, this process did not prove satisfactory for synthesis of SPEs for the food industry.
Some fatty acid esters of amylose, a very high polymer water soluble polysaccharide component of starch, have been synthesized and demonstrated to have many of the qualities necessary to make them low calorie synthetic fats [J. AM. Oil Chem. Soc., 39, 19 (1962) and 40, 551 (1963)]. These esters are only partially hydrolyzed and, in addition, only the fatty acid portion is absorbed through the intestinal wall making the caloric value of the materials very low.
Pat. No. 3,963,699 calls for solvent-free transesterification involving heating a mixture of a polyol containing four hydroxyls, a fatty acid lower alkyl ester, and an alkali metal fatty acid soap in the presence of a basic catalyst to form a homogenous melt, and subsequently adding excess fatty acid lower alkyl esters to the reaction product of that heated mixture to obtain the SPE. The polyol is any aliphatic or aromatic compound containing at least two free hydroxyl groups.
The need for low caloric fat-containing food compositions is also recognized in U.S. Pat. No. 3,579,548 (Whyte, 1971) of Proctor and Gamble, which discloses uses of triglyceride esters of alpha-branched carboxylic acids as low calorie fats. It is postulated that the alpha-branched carboxylate structure prevents the compounds from being hydrolyzed by pancreatic enzymes. Proposed uses are as fat replacements in salad oil, mayonnaise, margarine and dairy products.
U.S. Pat. No. 3,158,490 (Baur and Lutton, 1964) describes noncloudy salad oil containing esters of disaccharides in which there are not more than five unesterified hydroxy groups.
U.S. patent 4,034,083 (Matson, 1977) also to Proctor and Gamble discloses fortification of the SPEs with fat-soluble vitamins to form pharmaceutical compositions for treating or preventing hyper- cholesterolemia in animals, and for use in low calorie foods. This mixture is required because SPE ingestion alone causes vitamin depletion as noted above. Booth, A., and Gros, A., in a paper entitled Caloric Availability and Digestibility of New-Type Fats, Journal of the American Oil Chemists Society, Vol. 40, October 1963, pp. 551-553, disclose that in rat feeding studies amylose palmitate, amylose stearate and amylose oleate are only 17-29% digested. A related prior paper of Gros, A., and Feuge, R., entitled Properties of the Fatty Acid Esters of Amylose. Journal of the American Oil Chemists Society, Vol. 39, January 1962, pp. 19-24 discloses that these esters do not have sharp melting points and are extremely viscous when melted. The densities were somewhat greater than those of corresponding free fatty acids and glycerides. While the interest was for use as dip-type coatings in both foods and non-foods, no information appears to be available concerning the ability of these compounds to mimic sensory and functional properties of triglyceride fats in foods.
Canadian Pat. No. 1,106,681 (Trost, 1981) issued to Swift and Company relates to dialkyl glycerol ethers which are only absorbed in small amounts when fed to rats. Blends are said to exhibit the physical and organoleptic properties of conventional fats.
U.S. Pat. No. 2,962,419 (Minich, 1960), discloses esters of neopentyl type alcohols such as pentaerythritoltetracaprylate. The alcohols contain from 1-8 hydroxyl radicals and include at least one neopentyl nucleus while the fatty acids contain at least four carbon atoms. They were shown to be non-hydrolyzable by pancreatic lipase. Rats fed with these esters had lower levels of lipids in there serum. However, in demand feeding studies, rats which received these neopentyl alcohol esters ate more food than the control rats and thus there was no difference in weight gain among the two groups. Accordingly, it is possible that fat craving is stimulated by these compounds rather than satisfied.
Retrofats are esters of fatty alcohols with tricarboxylic acids It is reported that they are not hydrolyzed by pancreatic lipase and thus may have potential as non-absorbable fat substitutes. However, increased stool bulk resulting from ingestion of the non-absorbable retrofats is reported to be a potential drawback.
Alkyl esters, such as dodecyl ester of 2,3-ditetradecyloxypropionic acid have been suggested as a fat substitute but were found to be metabolized and absorbed in vivo rat study experiments. The alkyl ester group was split off first, followed by the alkyl ether groups.
As reported in JACS, Vol. 8 (1958) pp. 6338 ff and JAOCS, Vol. 36 (1959) pp. 667 ff, the USDA has synthesized a number of diglyceride esters of short chain dibasic acids for potential application in foods. Distearin glyceride esters of dicarboxcylic acids were found to be poorly digested and utilized by rats. Distearin adipate was almost completely non-digested while adipostearin was only 58% digested in rat feeding trials. In contrast, the oleostearin and dolein esters of dicarboxylic acids were more digestible and utilized. The symmetrical diglyceride esters of fumaric, succinic and adipic acids are more viscous than cottonseed oil and coconut oil. These may have use as pan greases, slab dressings or surface coatings for foods.
It is clear that there is a great need in the art for improved fat substitutes that are not only aesthetically satisfactory, but which are both easy and inexpensive to synthesize and do not have the disadvantages or negative side-effects of the prior art proposed compounds.